ControlSwitch's mask-sprite isn't working if it's part of a texutre sheet

When your mask sprite for the ControlSwitch is part of a texture sheet, the masking will not work correctly. One workaround is to save the mask-texture in a separate file.
Another solution is to render the mask sprite to a RenderTexture and use the rendered texture as the mask texture. I have successfully implemented this fix and can commit the patch, after the bug has been confirmed.